Arrhythmias Flashcards
What are the different types of arrhythmias
Tachy arrhythmias - fast
Brady arrhythmias - slow
Give examples of tachy arrhythmias
Atrial fibrillation
Ventricular tachycardia
Give examples of Brady arrhythmias
Heart block
Drug induced - Beta blockers, digoxin
What is the most common pulse in bradyarrhythmias
50bpm
Describe heart block
Slow or no conduction through the AV node to ventricles of impulse from SA node
What can be seen on an ECG of a patient with heart block
Prolonged PQ interval
What are the different levels of heart block and how are they classified
1st degree, 2nd degree
3rd degree - complete heart block as no impulse is passed to the ventricles
Classified by the length of signal delay
What is the correlation between heart rate and risk of arrhythmia
As heart rate increases, the risk of arrhythmia increases
How does ventricular tachycardia relate to ventricular fibrillation
VT is a precursor for VF
Describe the ECG of a patient with 3rd degree heart block
Regular P intervals but they are not necessarily tied to QRS complexes
Describe how atrial fibrillation appears on an ECG
Electrical activity arises throughout the atria rather than just the SA node
Narrow QRS, waves aren’t a fixed interval apart
No p waves as disorganised atrial activity
Irregular pulse - termed irregularly irregular
How does atrial fibrillation affect heart rate
Rapid atrial impulses conducted to ventricles giving high heart rate
How does ventricular tachycardia appear on en ECG
Broad QRS complex
Why is ventricular tachycardia particularly dangerous
Can lead to ventricular fibrillation and death
What abnormality occurs in the cardiac conduction system in AF
Many P waves are trying to get through to the ventricle through the AV node, but the AV node is only allowing a small number through
What abnormality in the cardiac conduction system causes VT
The time taken to activate the ventricular muscle is longer and as soon as it is finished, it starts again
This leads to electrical activity becoming uncoordinated
No coordinated muscle activity to allow the heart to work as a pump
What are cardiac pacemakers used to treat
Bradyarrhythmias
What is the purpose of a cardiac pacemaker
To keep the heart rate at a minimum level
How is a cardiac pacemaker fitted
Box fitted in chest wall on left side
Wires are passed through the vena cava, through the atria, one placed within the atrial wall another placed in the ventricle to trigger ventricular contraction
How do cardiac pacemakers work
Stimulate heart action by pacing atria and ventricles in sequence
Which dental equipment should be avoided with patients with pacemakers and why
Induction scalers as they generate a strong EM field
What has a theoretical risk of shutting a cardiac pacemaker down
Electrical fields such as an MRI or diathermy
When is an implanted defibrillator useful
Useful for patients with unstable cardiac rhythms
Where is an implanted defibrillator placed
Subcutaneously on the right side
How does an implanted defibrillator work
Has wires passing to the heart and will look for evidence of VF
Where there is, it will use a low energy pulse to coordinate the electrical activity and shock the heart out to VF very rapidly
What cardiac rhythms should I be able to recognise
Sinus rhythm
Asystole
Ventricular Fibrillation
In what cardiac arrhythmias do i need to know their clinical presentations
Atrial fibrillation
MI
What does the P wave correlate to in sinus rhythm
Atrial depolarisation
What does the QRS complex correlate to in sinus rhythm
Ventricular depolarisation
What does the T wave correlate to in sinus rhythm
Ventricular repolarisation
Why is the P wave in sinus rhythm small
There isn’t much muscle in the atria
Why is the QRS complex in sinus rhythm narrow and large
The bundle of His carries the electrical activity to the whole ventricle muscle very rapidly so the muscle contracts in a single unit creating a large electrical signal
How is ventricular fibrillation treated
Defibrillation
Describe ventricular fibrillation
No cardiac output
Electrical heart activity but disorganised
Muscle fibres contracting in ventricles at random so there is no emptying of ventricles
What can cause ventricular fibrillation
Heart attack
Electrocution
Long QT syndrome - can be drug induced
Wolf-Parkinson-White syndrome
Describe asystole
No cardiac output
No electrical activity
Defibrillation not possible
Low chance of survival
How can a patient in asystole be treated
Treated with adrenaline to try and produce some electrical activity in the heart so that a defibrillator can be used - tends not to be successful
